Radio frequency matching transformer



Feb. 16, 1954 v, 35 N 2,669,698

RADIO FREQUENCY MATCHING TRANSFORMER Filed April 26, 1951 2 Sheets-Sheet l IN V EN TOR.

BY Vina-n1 R 0:; one

ATTORNEY Feb. 16, 1954 v, 5 G 2,669,698

RADIO FREQUENCY MATCHING TRANSFORMER Filed April 26, 1951 2 $heets-$heet 2 I l 41 IT '1 INVENTOR.

BY Vlncuvr R. Duonq A 5* TOQ'NE y Patented Feb. 16, 1954 RADIO FREQUENCY MATCHING TRANSFORMER Vincent R. De Long, Cedar Rapids, Iowa, assignor to Collins Radio Company, Cedar Rapids, Iowa,

a corporation of Iowa Application April 26, 1951, Serial No. 223,090

3 Claims.

This invention relates in general to impedance transformers and in particular to inductance coilswound and connected so as to-obtain a desired impedance transformation.

In the electrical field it is oftentimes desirable to make an impedance transformation so that an output atone impedance may be connected to an input with a different impedance. In order to; prevent a discontinuity occurring when such a connection is made it is. desirable to place in the lineand impedance transformer which will eliminate thediscontinuity. For a more complete discussion of the theory of matching transformers reference may be made to Patent 2,470,307 issued to Guanella on May 17, 1949, entitled High Frequency Matching Transformer. Aplicants invention constitutes an improvement in. the manner of winding the coil and a new manner of connecting coils so as to obtain different impedance. ratios has been developed.

It is an object of this invention to provide an impedance transformer by utilizing two or more inductance. coils of this invention.

Another object of this invention is to provide a-coil: with high surge impedance which has op- Dosite sides of the line wound in the same directionabout acoil form whilev maintaining arelatively large distance between the turns of one side of the line and the turns of the opposite side of theline.

Yet another object of. this: invention is to provide an improved high impedance. coil which has opposite sides of the line wound about it in the same direction with relatively large spacing between turns of the opposite sides of the lines and with more than'one turn of each side made between turns of the opposite line.

A feature of'this invention is found in the provision for a new and novel coil which may be connected'invariousmanners to obtain difieren-t impedance transformations.

Further objects, features and advantages of this invention will become apparent from the following description and claims when read in view ofthe drawings, inwhich:

Figure 1 is an air view drawing of the coil of this invention;

Figure 2 illustrates a connection for making a 9-1 impedance transformation; and,

Figure 3 illustrates a connection developed by applicant for making a 9-1 impedance transformation.

With reference to Figure 1 a coil form, designated generally as I0, may be made of ceramic material, for example, and has attached a longitudinal insulating strip I I which might be formed of polystyrene, for example.

A pair of input terminals I2 and I3, respectively, pass through one end of the insulating strip II and fasten to the form ID to hold the insulating strip rigidly to it.

Output terminals I4 and i6, respectively, pass through the opposite end of strip II and attach to the coil form In.

One side ll of a line is attached to terminal L2. Conductor I 1 passes through a diagonal slot I8 formed in the insulating strip I I and is wound about the coil form to make a first turn I9, passes over the insulating strip I I in a slot 2i and makes a second turn 22 about the form 50.

After the second turn 22 the conductor is received in a slot 23 formed in the insulating strip II and passes diagonally across the strip for a substantial longitudinal distance from the second turn 22 and is wound about the form to make a third turn 24. A fourth turn 26 is made about the form IIl'by crossing over the insulating strip II.

After the fourth turn the conductor to output terminal I4 passes diagonally along the strip II.

The. other side. 21 of the line is connected to input terminal I3 and passes under the insulating strip II through a diagonal slot formed therein to emerge for a first turn 28. A second turn 29 is made by allowing the conductor to pass under the insulating strip II through a slot 3| formed therein. After turn 29 the conductor passes through a transverse slot 32 formed in the under side of the strip EI and passes asubstantial distance down the strip I I to emerge and make turn 33 which is the third turn for the second conductor. A fourth turn 34 is made by the second conductor. After the last turn 34 the second conductor is connected to the output terminal 6.

The longitudinal spacing between opposite sides-of the line increases the surge impedance of the coil and a practical size coil may be obtained. In other words, in order to get a relatively' high surge impedance, a much smaller coil will be needed when wound as shown in Figure 1 than when the opposite sides of the line are spaced relatively close together.

An advantage obtained by spacing two turns of the same side of the line close together is to increase the surge impedance by increasing the mutual inductance between adjoining turns of the same line.

A coil wound such as shown in Figure 1 has the characteristic that it oifers no impedance to balanced current flowing through the coil, but a high impedance to any unbalanced current. This is true because with a balanced current opposite sides of the line will carry equal and opposite current and the total inductance will be substantially cancelled for the reason that the conductors are wound in the same direction.

Unbalanced currents, however, flow in the same direction through both sides of the line and the inductances would add and thus form a high impedance path. As shown in the patents to Guanella, previously referenced, impedance transformations may be made by connecting two or more coils in the line. For example, Guanellas Figure 6 illustrates a connection for two coils to obtain a 4-1 impedance transformation.

Applicants Figure 2 illustrates means for obtaining a 9-1 impedance transformation between input terminals 36 and 3'! and output terminals 38 and 39. If the impedance of each coil is Z, the total impedance between the terminals 36 and 31 is 32. The rectangles 4!, 42 and 43 each represent coils such as shown in Figure 1 and are connected as shown in applicants Figure 2 which is the same as the right part of Figure 7. of the Guanella patent. Applicant has discovered, however, that an impedance transformation of 9-1 may be made with the connection as shown in Figure 3 with two coils 44 and 46. This may be shown by considering the unbalance currents represented by arrows placed adjacent the coils in Figure 2. It is to be seen that the unbalance current flowing in the middle coil 42 will be cancelled and therefore, the coil 42 has no efiect on the unbalanced currents.

This suggested to applicant that the coil 42 might be eliminated and the connections made as shown in Figure 3. In this case input terminals 41 and 48 are connected to windings 52 and 53, respectively, of coils 44 and 46. The opposite ends of windings 52 and 53 are connected to output terminals 49 and i. The second winding 51 of coil 44 has its end adjacent the input terminal 41 connected to output terminal 49 and its opposite end connected to output terminal 5|. The second winding 58 of coil 46 has its end adjacent the input terminal 48 connected to the output terminal 5| and its opposite end connected to the output terminal 49. With this connection the impedance transformation is 9-1 but only two coils 44 and 46 are used instead of the three coils shown in Figure 2.

It is seen that this invention provides a new and novel way of winding a coil so as to obtain a high surge impedance and also provides a new connection for two coils to obtain a 9-1 impedance transformation.

Although this invention has been described with respect to a preferred embodiment thereof, it is not to be so limited as changes and modifications may be made therein which are within the full intended scope of the invention as defined by the appended claims.

I claim:

I. A coil having a very high impedance to unbalanced currents comprising, a generally cylindrical coil form, a longitudinal insulating strip attached to the surface of said coil form, a pair of input terminals connected to one end of said insulating strip, a pair of output terminals connected to the opposite end of said strip, one side of a line connected to one of the input terminals and Wound about the coil-form over the insulating strip for two turns, said one side of the line passing diagonally down said insulating strip on the top after the second turn and wound about the coil form third and fourth turns, said one side of the line passing diagonally over the insulating strip to one of the output terminals after the fourth turn, the other side of the line connected to the second input terminal and passing diagonally under the insulating strip to apoint intermediate the sec- 0nd and third turns of the first side of the line, said second side of the line forming two turns about the coil form andipassing under the insulating strip, the second side of the line passing diagonally down the insulating strip after the second turn and coiled about the form to form another pair of turns, and said second side of the line connected to the other output terminal after the last turn.

2. A coil having high impedance to unbalanced currents comprising, a generally cylindrical shaped coil form, a first conductor wound about the coil form in pairs of turns longitudinally offset from other pairs of turns, an insulating strip attached longitudinally of the coil form and crossing over the first conductor, a second conductor wound over the insulating strip and about the coil form in pairs of turns longitudinally oiiset from other pairs of turns, and the pairs of turns of the second conductor Wound mid-way between the pairs of turns of the first.

cent pairs of turns.

VINCENT R. DE LONG. Y

References Cited in the file of this patent UNITED STATES PATENTS I Date Number Name 1,782,444 Ramsdell Nov. 25, 1930 2,178,653 Slade Nov. 7, 1939 2,301,023 Darlington Nov. 3, 1942 2,337,965 Boole Dec. 28,1943 2,470,307 Guanella May 17, 1949 2,522,370 Guanella Sept. 12, 1950 

